Many corrosive agents are present in the fluids produced from oil and gas wells. Although varying in concentration from place to place, these corrosive agents are known to cause damage to the metallic components of such wells if unchecked. Production tubing, because of its continuous exposure to produced reservoir fluids, has been found to be particularly vulnerable to damage. To inhibit corrosion, well-known treatment chemicals are commonly introduced into the annulus formed between the well's production tubing and casing, the chemicals then flowed toward the bottom of the well and returned to the surface with the produced fluids. In this manner, the life of vulnerable pumping equipment may be extended and well downtime reduced considerably.
In other producing oil and gas wells, paraffin or scale build-up is a problem. Paraffin, a waxy solid deposited upon the walls of well fluid containment surfaces, commonly obstructs the flow of fluid within the tubing, flow lines, and other related components of the well. Similarly, scale deposits having a variety of compositions are known in certain areas to form on production equipment surfaces, sometimes substantially reducing the performance of downhole pumps and the like. As with undesirable corrosion, paraffin or scale build-up may also be checked by introducing appropriate chemical treatment fluids into the wellbore.
Typically, the volume of well treatment fluids used to treat a hydrocarbon productive well is small. Amounts ranging from several milliliters to several liters are usually employed during each treatment. Because small fluid volumes are somewhat difficult to transport, it is frequently necessary to utilize auxiliary fluids for flushing the chemicals into the wellbore and to insure adequate distribution over the surfaces to be protected.
In treating a well, a predetermined volume of treatment fluid is introduced into the wellbore at regulated intervals of time. Depending on the severity of the conditions to be alleviated, the treatment fluid may be introduced into the wellbore on an hourly, daily, or even weekly schedule. The actual treating period during which the treatment fluid is maintained in the well may range from several minutes to several hours.